Brake pads and brake shoes include friction material which progressively wears away as the brake is used. Electromechanical wear sensors are known which can determine the amount of friction material wear and provide an indication to an operator that the brake pads or shoes require replacement. EP0877872 shows a sensor which monitors the movement of a brake component which moves in proportion to brake pad wear. The sensor outputs an electrical signal indicative of an amount of brake pad wear. Such a system relies on the progressive movement of the internal brake mechanism.
EP2650556 shows a brake assembly which is air actuated and has an adjuster driven by an electric motor.